Author Topic: How to wire a robot with 2 12v batteries and 24v motors and be able to charge  (Read 1788 times)

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Offline branfrdTopic starter

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I've refurbished an old robot from the 80's and I don't know what exactly is the best way to wire everything. The reason why I am having an issue is because I have the 2 12v batteries which need to be in series for the 24v motors and I have a 12v monitor and a 12v to 5v dc converter which powers the raspberry pi. Both of the batteries are lead-acid so I can't charge them in series, but I need to charge them without taking each one out and plugging them in. So how would I wire this?

Offline mklrobo

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 :) Hello!
I can offer an opinion from a vehicle application.
24V diesel vehicles/generators charge their batteries with
24V across the batteries, (both) with everything else attached.
Any sub-attachments acquire their power through voltage regulators
for that application. In this case, it would not hurt to have overvoltage
and surge protection for sub-attachments. Good Luck!!  ;D ;D ;D

Offline Billy

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So how would I wire this?

I had a similar situation once but was using Lithium batteries, but my solution should work with lead acid as well if the chargers you are using have a smart current based charging algo.

It requires two 12 volt chargers, with isolated secondary circuits. Isolated meaning that neither of the output wires is connected to anything else including the ground line in the power cord.

Then it's really simple: charge one battery with one of the chargers and the other battery with the other charger. You do not need to disconnect the batteries.

Yes I know this means the chargers are connected in series as well, but the charging current for each battery is still controlled by each charger....more or less.  In your case if you switch off the power before charging then the current is exactly controlled by each charger. If you leave the robot powered, then I'm not sure the current is 100% deterministic.

When I used this method, the robot remained powered while charging and I never had any issue, but I had checked the chargers for noise prior to using them and found the output very quiet.  And just to be sure I didn't burn the house down I had thermal fuses sandwiched between the batteries. Since you're using lead acid the risk of fire due to overcharging/uncontrolled charging is very low.


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