the best voltage to charge at 36 volt system?

[johnny reb]

this may sound confusing but here goes. a while back a guy who worked on carts n fork lifts (now retired) told me to discharge the batteries. i read to not discharge them fully. ok now i use true voltage meters on all the battery carts we currently have. ie xx.x volt
http://www.ebay.com/itm/36V-Golf-Car...xVCHKP&vxp=mtr
display.
so if you don't fully discharge them, at what voltage do you and is that sitting still or moving? sitting is say 37.1 sitting and 35.6 moving.

disregard the moving readings
3P's
Play
Park
Plug

never go below 36.3 volts at rest reading





good reading

http://www.cartsunlimited.net/Batter..._Tutorial.html

[scottyb]

All research and current understanding of wet cell lead acid batteries show that this type battery has no memory and there is 0 benefit from any deep discharge. In fact these batteries benefit from being kept as close to fully charged as possible.

[JohnnieB]

There are three voltages associated with the deep-cycle, lead-acid, wet-cell batteries typically used in golf carts.
1. On-Charge: The voltage while the charger is charging the battery.
2. Under-Load: The voltage while amps are being drawn from the battery.
3. At-Rest: The voltage about 12 hours after the charger shuts off, or about an hour after amps cease to be drawn from battery.

The On-Charge voltage varies from whatever the battery voltage is before the charger is connected up to anywhere from about 44V to about 48V depending on the charger type and the battery manufacturer.

The Under-Load voltage varies from whatever the pack voltage is before amps and decreases about 1.0V per 100A of current draw for a 36V pack. That amount is for the internal resistance of batteries themselves, the interconnecting cables have resistance, so the total drop will be more.

The voltage on your real time battery meter will vary up and down considerably while driving your cart since the amount of amps drawn varies considerably while driving. It drops fast as the number of amps drawn increase and recovers slowly when they decrease.

With a 36V pack, it is best not to routinely drop the voltage below 31.5V and you never want to drop it below 27.0V. (That is where irreversible physical damage to the plates begins.)

The At-Rest voltage is used to estimate the SoC (State of Charge) using the chart CDT posted. (Which is for Trojan brand batteries and clones)

The reason for letting the batteries rest for a period of time before you have a valid voltage to look up on the chart is because the batteries acquire a "surface" charge while charging. There is very little usable energy in the surface charge and the transition between the On-Charge voltage and the At-Rest voltage is non-linear and varies between batteries makes and models. It takes about 12 hours for the chemistry in the battery to reach an equilibrium after the charging has stopped.

The same is more or less true with the transition from Under-Load to At-Rest voltages, except equilibrium occurs sooner. Again, the recover time is non-linear, but most of the recover occurs in the first 15 minute and most of it occurs within half an hour.

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As CDT and Scotty mentioned, the higher the average SoC maintained, the longer the batteries last.

[Volt_Ampere]

The only reason to discharge FLA batteries is to measure their capacity and that is only valid if the discharge simulates actual running conditions.

[johnny reb]

thanks. unfortunately I listened to wrong advice. and discharged them below 50%. oh well it wont happen again.

[Volt_Ampere]

Once isn't the end of the world but you got bad advice. There are some batteries (NiCads) that have a "Memory" effect that is reduced by cycling them down every once in a while. NiCads don't mind being almost 100% discharged but FLA batteries deteriorate when they are discharged even below 50%.