Varying on charge voltage problem!

When was the last time you put them on an EQ charge with generator?

US Batteries are odd guy out on charge voltages. They require higher voltages than any other lead acid battery. In a Solar application all three stages (Bulk Absorb Float) should be set to 2.45 vpc or:

14.7 volts in a 12 volt system
29.4 volts in a 24 volt system
58.8 volts in a 48 volt system

They further require an EQ charge at 2.5 vpc every 30 days after being fully charged on a regular cycle to be applied for 3 to 4 hours. EQ voltage would be:

15 volts on 12 volt.
30 volts on 24 volt.
60 volts on 48 volts.

These are popular cheap golf cart batteries, but they have two undesirable characteristics that have been learned the hard way by thousands of golf cart owners.

• They are a 2-year battery.
• Standard golf cart chargers are not a high enough voltage and do not have EQ modes requiring golf cart owners to by a new charger with Delta Bump Algorithm. Delta Bump means they charge at a constant current of C/10 until dV/dt (4 mv/cell per hour) which means the voltage rise slows down to 4 mv per hour. No Solar Charge Controller has that algorithm.

What all this means to you is your batteries have been undercharged every since you bought them, and in desperate need of an EQ charge, and resetting all your charge controller settings.

Exactly what he said:

Sunking, thanks for that. However. For rate first 6 months of the battery I was charging at 58.8, I then on the advise of US batt raised the charge voltage to 59.2, so no undercharging here, if anything i maybe over charging a touch.

I fully charge the bank everyday.

I also EQ the batteries once a month for 2-3 hours at 63 volts, also per US Batt, as they said it would be ok, from what your saying that EQ voltage is way to high and should be more around the 61volt mark, correct? I can EQ with my panels as I have 2400 watts of panels and only a 232ah bank. I only need my gennie on cloudy or rainy days, don't need it to EQ.

Also, my inverter has a build in charger, and the charger does not go any higher than 62 volt, and it under reads a bit so is more like 61,4 in reality, which I have been told is to low to EQ properly, which again is whyI use the panels.

Also, all my SG's were in spec the last time I checked all the cells. Was on a hot day about 14 days ago, the lowest cells being 1,270, rest were a bit higher at 1,275 -,1280.

When your battery cell voltages diverge as you listed, they need equalization.

You can pick out the low batteries from the bank, and charge them seperatly, and spare the entire bank from the high power EQ, but you need to recharge the low ones.

quick question to consider - are all of the batteries the same age?
and how are they connected for charging and discharging?

If US Battery is telling you to use higher voltages on a solar application, I have no problem with that as most manufactures do that for Solar. If you are having voltage variations at high voltages something else is going on.

I suspect one issue, but you have to answer for it. Are you by chance tapping the batteries? Say a 12 volt tap across two of the batteries to power a 12 volt device?

No, I am not.

Well if the batteries are 20 months old explains everything. I did not catch that. Nothing wrong as that would be normal for batteries that are in need of replacement. US Battery are two year batteries whether you use them or not. Their calendar life coupled with high operating voltages eat them alive and corrode the plates. Look in the bottom of the battery jar. Bet you see something that looks black sand or very dark mahogany. That would be your battery plates.

Keep in mind those batteries despite what they call them are hybrid batteries made for golf carts, not a true deep cycle battery. A slight step up is a 3 year Trojan T-105. They have slightly thicker plates so they last a little longer but still a hybrid battery. Trojan does make a real 5 year deep cycle battery called the T-105RE. Much thicker plates and 5 pounds more lead in them. Just don't use them in a golf cart because it would be faster to just walk or push the cart.

The attraction of US Battery Golf Cart batteries is they are less expensive than Trojan and have better acceleration performance. The thinner plates lower the internal resistance and coupled with slightly higher operating voltage can deliver higher currents needed for acceleration. The trade-off is shorter cycle life.

I first noticed the varying on charge voltage about 6 months ago when the batts were only 14 month old. So you telling me that despite that fact I am getting the correct SG per spec 1,265 per cell and higher, my batteries are done and need replacement?

I am told that they at spec so are still giving me full capacity and are in good condition etc, and I am in the process of adding a second string of the same batts. The t105 are used a lot here , and these us batt xc2200 seems to peform better most say than those t 105's !!

Thanks for all the info, it's just it is a 180deg from what us batt and other have advised me! Confused now!!

I already told you that, but the permoance is higher currents, not longer cycle life.

Warranty is a dead give away.

US Battery is 1 year from the date code stamped on the post. You likely bought them when they were already 4 to 6 months old.

Trojan T-105 is a Signature line and carries a 12/24 from time of purchase meaning first 12 months full replacement, and months 13 to 24 are prorated. The T-105RE is a Premium line and carries a 24/60 from time of purchase.

If you want top of the line quality then Rolls Series 5000 is king with 36/120

Don't confuse Performance with Quality as that are not the same thing. Trojan is a much higher quality product than US Battery and is reflected in the price and warranty.

Ok so long story short, you say these batts I have are done, even though I have good SG. As I alwyas understood that when a battery was loosing capacity, the SG would start to drop off from spec meaning there was no longer enough active material to get the battery to full SG spec, hence a loss in capacity.

How do I know how long I have with this set?

Specific gravity is a measure of State of Charge, not capacity. The only way to determine capacity is with a capacity test which is beyond most DIY capabilites. Typically to save time one gets the Discharge curves fo rthe battery under test for the two-hours discharge rate then apply a C/2 precise load current and measure the time it takes to for the first cell to reach 1.75 volts. From that you take the Amps x Hours, then cross reference to the Discharge Curves provided by the manufacture.

For Golf Cart Batteries there is a special machine built specifically for golf cart batteries used to test for warranty claims. 6 volts cells have a 75 amp load applied, and 8 and 12 volt batteries use 50 amps. If the battery has at least 50% capacity is a pass.

There are a few failure modes for FLA but the 2 most common failure modes are sulfated plates from chronic under-charging and normal aging. The other is plate corrosion from chronic over charging.

Sulfated batteries is just a normal process where the lead sulfate crystals harden on the plates over time. As soon as the battery is less than 100% SOC the process begins. If you do not discharge too deeply, most of the soft crystals are dissolved back into solution with a charge and periodic EQ charges. But not all of them can be dissolved. Once hardened, they cannot be removed. What happens is the crystals accumulate and resistance begins to rise. Once high enough the battery specific gravity begins to go down because you cannot charge the batteries.

Plate corrosion is the exact opposite of sulfation. It is a Over Charge condition. That over charge corrodes the plates and they begin to flake off. As that happens you loose capacity because of loss of plate material, but Specific Gravity will be good, a little too good at times when you finish a charge cycle. Eventually as the plates corrode you wil start to notice the capacity is not what it use to be, and eventually unusable.

So what do you do? Continue to use them until they become unusable. But last thing you want to do is add new batteries to old batteries. Wait until your old batteries are boat anchors, then replace them. In the meantime do some research on batteries and the manufactures, and save some coins to buy the best you can afford.

US Battery is popular because they are inexpensive and have fairly low internal resistance. Low internal resistance is very important in high current applications like a golf cart. If you put in a new set of US
Battery in one golf cart, and Trojans in another identical cart, the cart with US Battery will accelerate quicker, but will go no faster then the Trojan. But the cart with the Trojan batteries will last a year or two longer than the US Battery. That is the trade-off between performance and quality.

Now here is the morale of the story. In a Solar System you do not need high performance or high current on discharge. You are not pulling 500 amps to accelerate or go up a hill. You are just pulling something less than C/10 at max for very brief periods of time. Most of the time pulling less than C/20. You do not need or want performance, you want cycle life. You cannot have both with Lead Acid. Well not that you can afford anyway. For that requires Industrial grade batteries used in Fork lifts. But those are even a waste of money in a solar system. You can get the same cycle life with good RE batteries for 1/2 the price. You don't need the performance side at twice the cost because you never use it.

Thanks for all the info Sunking, totally shocked that these batts are one the way out. They were sold to me as a better alternative to trojan t105. I am very surprised to hear they are though of as a lesser batt and more budget option as here is South Africa, they are almost the same price, about $190 dollars odd each, so not so budget here.

I have chatted to us batt at length regarding the cond and state of the batteries and told they are still fine and per new spec according to Mike at thier Georgia office, and to go ahead and add the second string and I would loose a bit of life long term but nothing to drastic.

Seems you have a very very diff take on the matter. I really do need more capacity as I am taking 4-5kw a night in summer and 3-4 in winter, not including the power the inverter uses, and that's tyring, I would like a little more room to breath. So I am at a bit of a lose at the moment as what to do,

I am thinking maybe I go lead crystal, they are avail here 12v 200AH. Just keep on using the current bank and maybe caring less about dod and using what I need and when they are gone then that's it.

How long do you recon I have left to support the loads mention above?

You are welcome, but don't get to worked up about it. As for pricing both Trojan and US Battery are made in the USA. Going rate for a T-105 here is $130 to $140 per unit. The US Battery equivalent 2200 XC2 is slightly higher capacity of 232 AH (7 AH more than the T-105) going rate $105 to $115 or about 18% less than the Trojan. US Battery are not bad batteries, they just are not Trojan. Don't go away thinking Trojan is the best, because they are not. FLA battery prices in the USA have a wide price range from 6-cents per watt hour on the low end, and up to 24-cents per watt hour on the high end. In the USA US Battery and Trojan weigh in around 7.8 cents and 10 cents respectively. The mistake people make which is understandable is they come away with the US Battery is a better value because it cost less per unit. But that is short term thinking because in application the Trojan is a far better value in the long term because they are going to have 50% more cycle life.

If you look at your Kwh cost is where it counts over the life of the battery. If you use 20% capacity daily from each battery, and assume the US Battery last 2 years, and the Trojan last 3 years, your battery Kwh cost are:

US Battery = $110 / [.278 Kwh x 730 days] = $0.5421/Kwh
Trojan Battery = $130 / [.27 Kwh x 1095 days] = $0.4566/Kwh

As you can see in this calculation Trojan is a better value.


Moving on to your situation you state cell voltage are 7.1 on the low end and 7.7 on the high end right? If correct that is troubling as that means your cell voltages range from 2.37 vpc up to 2.57 vpc. That is a huge difference. But let me ask you this. How and when are you taking those measurements?

If you are taking them while the batteries are charging or discharging is invalid results and what US Battery may be thinking. Voltage measurements are only valid on a rested cell that is not being charged or discharged. In other words disconnected and allowed to rest a few hours. So let's shift our attention away from voltages and use the only true measure of a battery SOC by measuring the Specific Gravity which can be done anytime. So what is the spread from high to low? If less than .030 points, then there is no problem. If more than .030 points they equalized. If they will not equalize the batteries have a problem.

Have you ever spilled any electrolyte? Have you ever charged too fast causing electrolyte to bubble or boil out? If so you have lost acid, and those cells will forever have a low specific gravity because you replaced acid with water.

As to your last question of how much more time do you have. Heck I do not know. Maybe 6 months... When you start to notice loss in performance, then you know it is time to replace them.