Hope someone can help . I have a synapse 3.0+ with 2 x100ah batteries.  I want to buy 2 more batteries but was thinking of 2x200ah  . Can I use 2x100ah and 2x200ah together? Will a battery balancer work?

Thanks 

One should not be mixing batteries of different capacities. They will charge and discharge unevenly. A balancer would even out batteries but remember balancers shuffle tens of Watts between batteries not the hundreds of Watts needed in your envisioned scenario.

23 hours ago, barendkoorts said:

Hope someone can help . I have a synapse 3.0+ with 2 x100ah batteries.  I want to buy 2 more batteries but was thinking of 2x200ah  . Can I use 2x100ah and 2x200ah together? Will a battery balancer work?

Thanks 

Although it can be done and there are reasons for not doing it with ever combination. 

If you check each present one for capacity and they are about the same I will do it purely for the much longer run time. I would just keep an eyes on the older 2 to get in early when either one loses capacity. Do a test once a 6 months. 

As far as the new and old charging / discharging at a different rate both will catch up to the same level. I would also 1st parallel the 100 and 200 to become one big battery before doing the series connection. Further I think Chris is talking about some balancers working at a few Watts. The more common type on sale at present balance at around 8-10A and don't only start to work at the upper voltage level. 

Further I will add a voltmeter to each battery to see when at different voltages so that you can manually balance if you don't use a balancer. I am doing just that on my 12V lithiums in series. Lithiums now in use for 15months and they don't go out a lot even if cycled every day. May be I am just lucky but I see the voltage of each one about 10 times + a day and can act if needs be. 

Some guys might fall off their chairs but I have also used lead acid and lithium in parallel for a few months. It was interesting to see how each type charges and discharges during use. I still had the combined capacity of all the batteries. Not to be done unless you charge each type to its correct level before closing a switch to put in parallel.