Adding a 2nd battery in parallel to original. Apollo Transport 24v

[Beansprout]

Adding a 2nd battery in parallel to original. Apollo Transport 24v
I just ordered a new battery from China, it claims to be 30Ah, and have a Battery management system (fingers crossed it does!)
The original is only 9Ah
Will i get away with connecing it in parallel
I have a volt reader
Probably should install a switch if onecan be recommended?
Hopefully the controller will be ok with extra power/reduced internal resistance of batteries?
Perhaps should only run at half power when battery fully charged
Thanks!

Pardon our interruption...

 

[sjpt]

I think the 30Ah claim is probably rubbish.
I'd be very cautious joining them in parallel, even if you could ensure they were equally charged (to within 0.1v or so).
People have paralleled batteries with appropriate diodes to prevent the problems of one trying to charge the other; someone may be able to point you at the appropriate thread.
A switch should be OK, as long as you were 100% sure there wasn't a point where they were both connected at once.
I'd just connect one at a time; much simpler

 

[thelarkbox]

Hi welcome, and can you cancel ?? printing bullshit on the label is a Huge red flag and 30ah with dimensions and mass smaller than a valid 10ah battery at 1/2-1/3 the price of a battery with a more trustworthy supply chain.

 

[AntonyC]

When batteries with different types, capacities or condition (age etc.) are paralleled, even at the same voltage, there can be substantial cross-current between them during use, which detracts from their performance / adds to their stress (ageing or failure rate). They need a dual battery adapter to get the most out of them. A bridge rectifier and heatsink can be cheaper but doesn't give the full benefit.

With a budget battery there's more reason than usual not to bring the bike in the house.

Edit: you need to be quite choosy with a switch, an adapter's a surer way of getting a decent result.

 

[saneagle]

Adding a 2nd battery in parallel to original. Apollo Transport 24v
I just ordered a new battery from China, it claims to be 30Ah, and have a Battery management system (fingers crossed it does!)
The original is only 9Ah
Will i get away with connecing it in parallel
I have a volt reader
Probably should install a switch if onecan be recommended?
Hopefully the controller will be ok with extra power/reduced internal resistance of batteries?
Perhaps should only run at half power when battery fully charged
Thanks!

Pardon our interruption...

What you've bought is a 7S3P pack or recycled cells. 3P means between 6.6 and 10Ah, depending on what cells they are. If they've added up the individual cells' capacity to get 30Ah, it would mean that the cells are 1.5Ah each and the pack is only 4.5Ah, which would be about right for recycled cells.

The dimensions don't seem to leave enough space for a BMS, and the pictures show no such bulge, which would make it quite dangerous to use. The BMS is a separate circuit board about 3 inches square and 5 - 10 mm thick, which should be lying against the cells under the heatshrink. If you cannot see or feel that, do not use that battery until you fit your own BMS.

It is possible to connect batteries in parallel, but there are a few things to look out for, and I don't think it's a good idea to do anything with the one that you've ordered other than break it open and use the cells for powerbanks. You can buy the empty powerbank cases on Ebay:
1. You must not charge batteries while they're in parallel because one will charge the other through its output, by-passing the charge controls.
2. You must only connect them when they're approximately at the same voltage. Anything within 1.0v would probably be OK, but the nearer the better.
3. You can make them much safer by using blocking diodes so that one can't charge the other.
4. You cannot put any normal switch on the power wires because the controller's inrush will burn it.

 

[AntonyC]

There's a small bulge in the third photo showing dimensions but definitely inspect the pack on arrival regardless of what the advert says.

 

[saneagle]

There's a small bulge in the third photo showing dimensions but definitely inspect the pack on arrival regardless of what the advert says.

That looks like the wire to me going from one end of the pack to the other. Right at the bottom of the listing, it says battery pack with BMS. You need to check because it's the difference between a safeish battery and one that's likely to set fire to your house.