Battery charger temp compensator

[US1Fountain]

I’ve replaced my old charger with a 3 bank charger with the temp probe. I’ve seen reference to installing the probe on the battery bank that will see the highest ambient temp such as next to a heat source such as closes to an engine. Also seen recommendation to install it on a house bank which will see the most activity. Any thoughts on the best setup? I’m using all 3 banks for my Gen and both motors. House load is pulling off 1 motor bank. My confusion comes from the probe only allows to monitor 1bank. What’s to keep from the other non monitored banks from overheating ( shorted battery cell) and the charger going into full output thinking that bank is only at 10V?

Also, I need to extend the probe wiring to avoid running it in path of traffic. It looks like the plug end is a standard home RJ11 jack type. I have the tool and ends for that if so can this temp probe be extended with a simple extension cable?

[a64pilot]

Nothing protects you from a bad Cell, to do that you would need to monitor every battery at least and likely each cell.
I would attach to the bank that gets the most use, it’s only going to get warm under charging most likely.
Best use of mine so far is it turns up the charge voltage in cold weather, I have yet to see it reduce the voltage by much, but haven’t been in extended hot weather.

[john61ct]

Yes to extending, just keep the pinout order.

Put it on the house bank, one you care about more, expensive, deeper cycled. Adjusting the voltage for optimum charging is the point.

Batts actually getting heated by the engines will wear out faster anyway.

[a64pilot]

Extension wise, I have just ordered the correct length telephone cable so I have no splices. Put some silicone grease on the connectors to prior to plugging them in, especially if there is an end in the battery compartment.
If you have to splice, then there are of course inexpensive dual female connectors.

[US1Fountain]

Thanks!

[Dadrock33]

US1Fountain - check out this link: https://marinehowto.com/installing-a...ttery-charger/ It's a bit of a read but you'll find your answer in there on the temperature probe (hint: attach to negative terminal on the most active battery or the battery that heats up the most [like next to an engine heat source]) That link is the Bible of things to do for our boats.

[Ahmet Erkan]

Originally Posted by a64pilot

Nothing protects you from a bad Cell, to do that you would need to monitor every battery at least and likely each cell.
I would attach to the bank that gets the most use, it’s only going to get warm under charging most likely.
Best use of mine so far is it turns up the charge voltage in cold weather, I have yet to see it reduce the voltage by much, but haven’t been in extended hot weather.

FLA batteries float voltage is recommended to be compensated by -3mV/DegC/Cell rise in ambient temperature. This translates to 0.54 Vdc for a 12V battery subjected to a temperature rise of 30 DegC (ie: From 20C room temperature to 50C standard ABYC machinery space maximum temperature)
You may want to place the battery charger temperature probe in a glass of water and ice and record the float voltage when the voltage stabilizes and then take the probe out of the water at 0C and let it warm up to the measured room temperature, this test should validate if the charger temperature compensation is working properly.

[hzcruiser]

Originally Posted by US1Fountain

I’ve replaced my old charger with a 3 bank charger with the temp probe. I’ve seen reference to installing the probe on the battery bank that will see the highest ambient temp such as next to a heat source such as closes to an engine. Also seen recommendation to install it on a house bank which will see the most activity. Any thoughts on the best setup? I’m using all 3 banks for my Gen and both motors. House load is pulling off 1 motor bank. My confusion comes from the probe only allows to monitor 1bank. What’s to keep from the other non monitored banks from overheating ( shorted battery cell) and the charger going into full output thinking that bank is only at 10V?

Ideally your CC should be able to monitor each batt, not just each bank. If you only have one probe you could consider putting that on the smallest bank, assuming that would start heating up first.

A shorted cell can be detected by measuring each cell voltage independantly.

Originally Posted by US1Fountain

Also, I need to extend the probe wiring to avoid running it in path of traffic. It looks like the plug end is a standard home RJ11 jack type. I have the tool and ends for that if so can this temp probe be extended with a simple extension cable?

Some CCs measure temperature with a simple probe that changes its resistance with temperature.
Extending the lead will change the resistance, too. If you only need a few extra cm / inches, extending it shouldn't be a problem, if done right (crimped).
Using a (cheap) female-female RJ11 connector can mess up the temperature readings. Maybe not today but a few months down the road, due to movement of the cables, heat or corrosion inside the connector.

The better systems have the sensor and measuring on the probe itself and report it back to the CC via a digital signal, e.g. I2C or 1-wire. That can be extended more easily and if there is a problem with the wiring there, you'll get no temp reading, rather than a wrong one.

[US1Fountain]

Originally Posted by Dadrock33

US1Fountain - check out this link: https://marinehowto.com/installing-a...ttery-charger/ It's a bit of a read but you'll find your answer in there on the temperature probe (hint: attach to negative terminal on the most active battery or the battery that heats up the most [like next to an engine heat source]) That link is the Bible of things to do for our boats.

Yes, Ive read that. That is where I found the recommendation to connect the probe to the battery that will see the most outside heat. My manual recommends to connect to house bank. I can see both points, but as stated by a64pilot, I can only monitor 1 battery bank out of the 3, so it makes more sense to use the one with more activity, at least to me.
I need to extend the probe wires approx 2 feet. Or relocate the charger closer to the batteries, into the engine compartment. Now its located under the aft cabin bed where the AC, water heater, fresh and holding tanks are located. So its more of the mechanical area.
Charger is a Promariner ProNautics 1240.

[john61ct]

Never come across a so-called multi-bank charger that outputs different voltage per bank, basically they work just like an isolator or VSR.

Forget about separate temp sensing, need a separate charger for each bank for that.

And per-cell monitoring is only a high-end LFP BMS thing, hardly worth doing "live" for mere lead batts.