Solar charging

[Benjahmin]

I agree - it comes down to usage.
As an ex BT maintenance engineer I know that exchange batteries are floated, that is to say they are permanantly on charge.

They are mainly there as a smoothing device to take out/absorb transient spikes coming from the 50v power plant. They also provide a short period of exchange main load backup during mains failure, but this only lasts as long as it takes the generator to auto start and get to speed. So they are never deep cycled.
Given the far more reliable mains and electronic exchange equipment, I'm not even sure they still use this system.

 

[Andy-Mat]

I agree - it comes down to usage.
As an ex BT maintenance engineer I know that exchange batteries are floated, that is to say they are permanantly on charge.

They are mainly there as a smoothing device to take out/absorb transient spikes coming from the 50v power plant. They also provide a short period of exchange main load backup during mains failure, but this only lasts as long as it takes the generator to auto start and get to speed. So they are never deep cycled.
Given the far more reliable mains and electronic exchange equipment, I'm not even sure they still use this system.

What you said was fully correct, but some of the terms you used may not be fully understood by other members here.
For example, floating a (for example only a 12v nominal battery), sets a max voltage, so that the battery only charges up to a specified voltage level, usually well under what some term FULL = over 14 volts. Cars often charge up to around 14.5 volts. Causing the battery to gas.
This way the floating battery never gases, which is a further danger to life and limb as it not only dispels the water in the acid, but delivers a gas mixture of oxygen and hydrogen, very explosive, as many have found to their cost!
Floating, if done correctly, extends the life of LA batteries tremendously!

My style of "Floating".....
I used to set my caravan charger max voltage at 70% of the rated battery capacity, for say a 12 volt nominal battery, that would be somewhere around 13.2 volts. Different manufacturers specify different levels.
Also, I cut the load at around 11.6 volts, below which damage (starts) occurs to a normal LA battery, particularly if left below that for long periods, as I treated my leisure battery as a normal 12 volt, even though it was deemed safe to drop well below this......I sincerely believe that is why that battery lived so long (is still living!).

So under both the floating charge and any 12 volt loads, the battery would sit somewhere betweel 11.6 and say around 13.3 volts.....

Remember this was for a caravan, and it was charged either from the car alternator when underway, via the charger circuit, mains when parked, except when parked at a camping site with no mains (the best ones!), when I would either start a portable generator, or run the car engine for 10 minutes or so, every 3rd day or so.
I changed all the lighting to either LED type bulbs, or 12 volt tubes. Good light and low power drain. My SAT receiver/TV took the most power, but it was still acceptable.
The car I used for towing had a 120 amp alternator, and a second 12v battery for the Diesel heating system under the front passenger seat, so I had a lot of 12 volts available one way and another!
Memories!!!
regards
Andy

 

[matthewslack]

Any LA Battery, totally misused, will dissappoint the idiot that ran them like that.
The plus point on a Leisure battery, also often called a deep discharge battery for obvious reasons, is that if it is recharged reasonably quickly, it will live to charge another day. Say within 24 hours, no damage caused.
True car batteries are often wrecked completely if they are run down to nothing! JUST ONE TIME WILL DO IT!
Plus having some (relatively!) simple electronics to monitor the battery voltage and to cut off discharge at some preselected point, will of course prevent serious damage tp either type.
Read some of the documents I posted, you could learn a lot, if you so wished!
Have a nice day.
Andy

Many of those people are not idiots, they have simply relied too much on others and claims on labels.

Have you ever considered being a little less harsh in your posts? One thing I really like about this forum is its overwhelming helpfulness and lower than normal level of negative qualities. May I venture to suggest you could increase the sum of human happiness with some thoughtful pre-post reviewing?

 

[slowbutsure1936]

Numbers:

Your 48V 20Ah bike battery is around 960Wh, taking the label literally. The charge efficiency of lithium ion is close to 100%, so you need 960Wh plus a bit to allow for the charge controller efficiency from your solar for a full charge from flat. Call it a round 1000Wh, because you don't really want to run it completely flat.

If you need that every day, then you will need about 200W of solar panels: an average day between April and September will give you 4 or 5 Wh for each W of solar panel. A pure blue sky will give more than 10, I.e. 2000Wh from 200W panels, enough to charge two such batteries.

So your 150W panel, if in good working order, is reasonably close to that, so I would start with that and a cheap Elejoy controller for direct charging.

Indirect charging via a lead acid leisure battery, or better, a LiFePO4 lithium battery, needs more panel and a fairly large intermediate battery. I took two 40Ah, 4 cell so 12.8V nominal LiFePO4 buffer batteries with me on my Scotland to Wales ride last October, leaving home with them fully charged. 40Ah x 12.8V is 512Wh each.

I found that using a Sterling Power 150W quasi sine wave inverter and the standard Shimano 1.8A charger, each put only 80% into a flat 418Wh Shimano E8014 battery - just 330Wh or so - before the inverter reached its 10.5V low voltage cutout. That's only 65% combined efficiency from inverter and charger, which roughly equates to 80% efficiency each, which is plausible.

So to go that route, you would need 1.5 times as much solar panel for a start, and then enough buffer battery capacity to match the 1000Wh needed by the bike battery. At 12V, 1000Wh is just over 80Ah, so allowing for inverter and chargef efficiency, 120Ah of usable capacity is required.

As a general rule, going below 50% depth of discharge is not good for the life expectancy of lead acid leisure batteries, so assuming you always have a full leisure battery to begin charging, it needs to be at least 240Ah. However, in the real world, it will not always be full, so either it needs to be yet larger still, or a separate 'low voltage cutoff' device will be needed to protect it from deep discharge. The inverter will keep on going down to a horribly low cutoff, which will trash the leisure battery in a matter of months.

It is also necessary to allow for the poor round trip efficiency of lead acid batteries: you only get back about 70% of the energy used to charge, which translates to needing even larger solar panels. To get the same effect as the direct charging using your existing 150W panel, you would need to increase by 50% for the inverter and charger efficiency losses to 225W, and then by about 50% again to 340W for the round trip losses.

Summary:

Direct charging will do fairly well with your existing 150W panel, and needs only a charge controller and wiring to set up.

Indirect charging needs double or more solar panel, about 240Ah of leisure battery, low voltage cutoff device and suitable inverter.

If you can find another 48V battery that fits the same mount as the first, I think the two batteries, direct charging setup is probably the way to go.

Thanks thats a helpful summary. I do have two 120ah leisure batteries kicking around so I might try that route first, just as its cheap for me. I have been looking at putting LION cells together. My cousin has actually put together a 3.6kw battery doing this in his garage! Only weighs about 25kg apparently. Overkill for me, but it was interesting! If the leisure batteries don't cut it though, I think I will do as you suggest and get another 48v battery for direct charging.

 

[Andy-Mat]

Many of those people are not idiots, they have simply relied too much on others and claims on labels.

Have you ever considered being a little less harsh in your posts? One thing I really like about this forum is its overwhelming helpfulness and lower than normal level of negative qualities. May I venture to suggest you could increase the sum of human happiness with some thoughtful pre-post reviewing?

HARSH! No swear words, no picking on anyone in particular, just general terms.....If you feel picked on, you read that into it all on your own.
You should read some of the replies I get from people who could not find their pwn backside if given an hour or so to do it!
Some Pedelecers are more of a study for other people wanting to learn more, first hand, about the "Dunning Kruger Effect".
I wish you again, a great day.
Andy

 

[matthewslack]

Thanks thats a helpful summary. I do have two 120ah leisure batteries kicking around so I might try that route first, just as its cheap for me. I have been looking at putting LION cells together. My cousin has actually put together a 3.6kw battery doing this in his garage! Only weighs about 25kg apparently. Overkill for me, but it was interesting! If the leisure batteries don't cut it though, I think I will do as you suggest and get another 48v battery for direct charging.

Another route is the large LiFePO4 cells from CALB and others, 4 of them for a nominal 12V battery. Plus a BMS board of course. They are tolerant of deep discharge, and half the weight per Ah as lead, which means for usable capacity, about a quarter the weight. Also only 4 big cells to connect rather than a large number of li-ion 18650 or 21700. And very high cycle life, 2000 is not uncommon.

 

[matthewslack]

HARSH! No swear words, no picking on anyone in particular, just general terms.....If you feel picked on, you read that into it all on your own.
You should read some of the replies I get from people who could not find their pwn backside if given an hour or so to do it!
Some Pedelecers are more of a study for other people wanting to learn more, first hand, about the "Dunning Kruger Effect".
I wish you again, a great day.
Andy

Awesome! I'll take that as a no!

 

[cyclebuddy]

I do have two 120ah leisure batteries kicking around so I might try that route first, just as its cheap for me.

As you've got the batteries, for what you want to achieve, I'd just do that too. As @matthewslack points out it's not the most efficient, but it is a cheap, robust, safe solution that works.

For my 2 x 10.4Ah 36v ebike batteries, I've done it with an old 100Ah van starter battery, a cheap 100w panel, £20 solar controller off ebay, and a £40 sine-wave inverter. The (mobile) problem I had was the modest panel size/limited daylight time to recharge, but in a static/shed/garage situation, you have far more scope. Obviously, as you've already discussed, you're going to need something a little beefier for what you want to achieve, but given you already have at least the majority of the parts you need kicking around, it seems a no-brainer to me.

Good luck!

 

[Andy-Mat]

Thanks thats a helpful summary. I do have two 120ah leisure batteries kicking around so I might try that route first, just as its cheap for me. I have been looking at putting LION cells together. My cousin has actually put together a 3.6kw battery doing this in his garage! Only weighs about 25kg apparently. Overkill for me, but it was interesting! If the leisure batteries don't cut it though, I think I will do as you suggest and get another 48v battery for direct charging.

Just a small point, leisure batteries are really not for bikes anymore (were maybe used 20 years or so ago), far too heavy for the energy they store.

Until something better comes along, we are all stuck with Li-ion chemistries. But there are some interestiing developements in store over the next 10 years or so.

The trick to staying safER(!) with Li-ion Batteries are basically as follows:-
1) protect them at all times from physical damage and shock.
2) If not a well trained electrical engineer, do not "play" with them at all....
3) Always buy best quality cells in your Batteries. I myself like panasonic, but other good makes come to mind. "No name" batteries are to be avoided completely. Buying from shops that resell them can be fraught.....
4) Therefore always buy directly from the manufacturer....
5) If you decide anyway to try and make your own battery, or recell one you have, get 1st class cells, all from the same manufacturer, all of exactly the same type, all made on the same day, and all sorted by the manufactuer for exact compatability, charge all cells to exactly the same level before welding them together. YES, buy a battery spot welder to assist with the build.
Doing all that will usually reduce size/difficulty of some of the problems you may encounter.
This may prove instructive:-

I myself decided LONG ago, to only buy finished new high quality batteries, as I like the fact that I can count to 10 on all fingers and thumbs still!
regards for a great day
Andy
PS. As a test for anyone, do you all fully understand the difference between a battery and a cell? As I see some people dangerously mixing up the terms here on Pedelec!! As if they cannot get that right, what else are they mixing up?

 

[guerney]

If some of the troublesome BMSs have volatile memory which erase with loss of power, or some other method of resisting battery pack cell replacement - is a rapid switch (Schottkys) to an alternative power supply or battery pack viable, while the original battery pack has it's cells replaced? It's something I'd consider trying, if I owned an otherwise irrepairable Bosch ebike battery.

 

[guerney]

First of its kind off-grid e-bike charging station launches in Newcastle

Power Trip has started generating electricity at the Cycle Hub cafe on Newcastle's iconic quayside.

www.chroniclelive.co.uk

 

[GLJoe]

My style of "Floating".....
I used to set my caravan charger max voltage at 70% of the rated battery capacity, for say a 12 volt nominal battery, that would be somewhere around 13.2 volts. Different manufacturers specify different levels.
Also, I cut the load at around 11.6 volts...

So do you happen to know what was the original Watt/hour maximum potential of your battery (maybe quoted by the manufacturer?), and then what was the actual usable Watt/hour figure that you were getting when you used your method to extend its life ?

I suspect your method does work, but one would want to know how much actual usable capacity you are sacrificing, so one could then calculate how much extra capacity to factor in when initially purchasing a battery.

 

[slowbutsure1936]

Just a small point, leisure batteries are really not for bikes anymore (were maybe used 20 years or so ago), far too heavy for the energy they store.

Until something better comes along, we are all stuck with Li-ion chemistries. But there are some interestiing developements in store over the next 10 years or so.

The trick to staying safER(!) with Li-ion Batteries are basically as follows:-
1) protect them at all times from physical damage and shock.
2) If not a well trained electrical engineer, do not "play" with them at all....
3) Always buy best quality cells in your Batteries. I myself like panasonic, but other good makes come to mind. "No name" batteries are to be avoided completely. Buying from shops that resell them can be fraught.....
4) Therefore always buy directly from the manufacturer....
5) If you decide anyway to try and make your own battery, or recell one you have, get 1st class cells, all from the same manufacturer, all of exactly the same type, all made on the same day, and all sorted by the manufactuer for exact compatability, charge all cells to exactly the same level before welding them together. YES, buy a battery spot welder to assist with the build.
Doing all that will usually reduce size/difficulty of some of the problems you may encounter.
This may prove instructive:-

I myself decided LONG ago, to only buy finished new high quality batteries, as I like the fact that I can count to 10 on all fingers and thumbs still!
regards for a great day
Andy
PS. As a test for anyone, do you all fully understand the difference between a battery and a cell? As I see some people dangerously mixing up the terms here on Pedelec!! As if they cannot get that right, what else are they mixing up?

Thanks Andy, I will take that on board. I do want to go the cell route as one of the reasons im doing an ebike conversion is wanting to enjoy a project. It is the journey as much as the destination for me. I have got a "can do" attitude that gets me in trouble sometimes, but I will take on board what you say and watch a ton of videos before I start.