Lester Summit II Charging Question

[Ezgeaux]

Quick charging question. I just got a Lester summit 2 charger. I have six crown cr235 batteries (36v). I put this battery model into the charger connect app and selected the recommended battery profile of 22252 (was originally set on 22251). I plugged it in and went to sleep for the first charge cycle. I looked at the history in the morning and noticed the final voltage was 49.7V (seems high). These batteries are about 2 months old and I previously was using the typical ezgo powerwise charger. The powerwise charger seemed to cut off between 46-47V if I remember correctly.

This evening I drove the cart then did a second charge cycle with the new Lester charger and periodical watched it. Once it reached the end (phase 3) the batteries were hissing pretty loudly and I could slightly smell some of the off gas from the batteries. I can’t say I remember them making this much noise or producing a smell (never watched quite this closely though).

Is all of this normal or are my new batteries getting over charged? Or Was the old powerwise not charging them high enough?

See attached for crown cr235 data sheet with charging instructions. Also see attached for the 22252 profile recommended by the ChargerConnect app for my battery model.

Just want to make sure I’m not screwing anything up with my new batteries.

Thanks!

[JohnnieB]

The antique ferroresonant transformer type chargers, such as the Powerwise model 28115, simply shut off at about 45V, which was thought to be high enough not to undercharge new batteries too badly while not overcharging old batteries too much. In other words, a compromise reached because the technology needed to do charge both now and old batteries properly with the same charger that was available at the time, was too expensive to put into consumer grade product.

Now the price of dV/dT (change in Voltage over change in Time) technology need to fully charge batteries is less expensive and found in most modern chargers.

That said, the last line of Crown's charge instructions for their CR-235 on the spec sheet you posted says max end of charge voltage is 2.7VPC, or 48.6V for a 36V pack and it looks like the end of charge reached by your Summit-II was 49.7V. or 1.1V above the manufacturer's recommended max.

Looks like Lester & Crown need to communicate better on which charge profile should be used for which battery.

There is a phone number on the bottom of the Crown brochure, and a support page on their website, contact Crown and ask them which profile to use.

[Ezgeaux]

Originally Posted by JohnnieB

The antique ferroresonant transformer type chargers, such as the Powerwise model 28115, simply shut off at about 45V, which was thought to be high enough not to undercharge new batteries too badly while not overcharging old batteries too much. In other words, a compromise reached because the technology needed to do charge both now and old batteries properly with the same charger that was available at the time, was too expensive to put into consumer grade product.

Now the price of dV/dT (change in Voltage over change in Time) technology need to fully charge batteries is less expensive and found in most modern chargers.

That said, the last line of Crown's charge instructions for their CR-235 on the spec sheet you posted says max end of charge voltage is 2.7VPC, or 48.6V for a 36V pack and it looks like the end of charge reached by your Summit-II was 49.7V. or 1.1V above the manufacturer's recommended max.

Looks like Lester & Crown need to communicate better on which charge profile should be used for which battery.

There is a phone number on the bottom of the Crown brochure, and a support page on their website, contact Crown and ask them which profile to use.

Thanks JohnnieB. I will give them a call today. I should also mention that it does seem like my DVM is consistently about 0.8V lower than what the ChargerConnect app senses from the charger while connected and charging my pack. I wonder if I should obtain a measurement at the terminals to see what the voltage of the pack is at the end of charging to compare. Regardless I still want to confirm I am using the correct profile per crown.

[JohnnieB]

Check the battery in your DVM. They tend to loose accuracy when the battery is low.

Wouldn't hurt to see if you can get the voltage at the main battery terminals when charger shuts off.

I have DVMs with Min/Max functions that come in handy for doing stuff like that. I just let the meter do the watching while I do other things.

[Ezgeaux]

Originally Posted by JohnnieB

Check the battery in your DVM. They tend to loose accuracy when the battery is low.

Wouldn't hurt to see if you can get the voltage at the main battery terminals when charger shuts off.

I have DVMs with Min/Max functions that come in handy for doing stuff like that. I just let the meter do the watching while I do other things.

Nice that’s what I need to do! So I spoke with a crown rep. He didn’t seemed too concerned about the final voltage. He said 2.7-2.75 VPC is ok, and he would rather see it on the high side. I told him what my selected battery profile does. He did mention he would rather see the absorption a little higher (2.42 vs 2.39 of my current profile). Not really sure what that means. Finishing amps are roughly 3% of the 20 hr rating as he mentioned. Seems like everything is close enough.

He talked about doing a SG test possibly or something but I think I’m fine as is.

[JohnnieB]

A lead-acid, wet-cell, deep-cycle battery is not fully charged until the SG of the electrolyte ceases to rise while a charging current is passing through it. Since the battery's open circuit voltage tracks the SG of the electrolyte, it can be inferred that the battery isn't fully charge until the on-charge voltage ceases to rise while a charging current is passing through the electrolyte. What dV/dT (change in Voltage over change in Time) technology does is monitor the on-charge voltage and when the rate of increase drop below a stipulated amount, it terminates the charging process.

In addition dI/dT (change in Amps over change in time) as well as dV/dT may be used to progress from charging stage to charging stage.

There are typically three charging stages, Bulk, Absorption and Finish.

Bulk is typically a constant current stage. Usually around 10% to 13% of the AH at the 20 hr rate is held at that Amp rate until the on-charge voltage climbs to the Absorption stage voltage.

Absorption is typically a constant voltage stage. Usually about 2.4VPC. The voltage is held contestant as the Amp flow decreases down to about 3% of the 20 hr AH rating of the battery, then the charger transitions to the Finish stage.

Finish stage is constant current again. Held at about 3% of the 20 hr AH rate until the on-charge voltage stops rising or slow to a predetermined rate. IE: some battery manufacturers recommend 0.004V/hour/cell.

In other words, for the most part, the battery, not the charger, determines what the finish voltage reaches.