Battery Load Test

[Osprey]

My factory installed UB121100 AGM batteries have completed 7 years of service. They still seem to be okay but I would like to load test them before next season. To make the test one needs to know the MCA rating of the test battery. i.e. something like 700A. My difficulty is that the specifications provided by the brand ,UPG, do not include the MCA (or alternately the CCA) rating for these AGM deep cycle batteries. From time to time, posts to Tugnuts have mention having done a load test. Can someone post the value they used for the test?

 

[Chimo]

I wondered the same thing. I too downloaded the datasheet for these batteries and could find no CA rating. When I googled the battery I found it for sale at a few sites and a couple of them mentioned 535 CA rating. Where they got that number from I don't know but the reference does seem to be quite consistent [though that may mean it simply came from one source and got quoted by everybody]. I believe it does say on the battery itself replace after 3 to 5 years but given the cost of these things I'm really hoping for a longer life. Your experience is encouraging! My house batteries have twice been subjected to quite deep discharge. I know that AGM batteries are supposed to accept this better than conventional but time will tell. I think the good news is that I keep the boat in the boathouse and the batteries are permanently on float charge when I am not out cruising.

 

[Crewdog]

A test I used, but was time consuming, is to disconnect the batteries one by one, make sure they are fully charged, then hook up an inverter powering a 100 watt load, and measure how much time it takes for the voltage to reach 11.5 volts.

I had 4 batteries that showed good on a tester, but 2 only lasted for 2 or 3 hours before reaching 11.5 volts.

it takes about 1 amp of dc current for every 10 watts of ac from an inverter, so a 100 watt bulb will need 10 amps of dc.

If you leave the 100 watt bulb on for 5 hours, then that uses about 50 amp hours.

I did keep 2 batteries to use around the house for emerg power and jump starting, and 2 went to the recycler.

just my 2 cents.

good luck

 

[tugnnaweigh]

Batteries and trailers are the two most troublesome things in boating. I’ll step up and say getting seven seasons of trouble free service makes it abundantly clear you’ve been doing everything very very correctly and you’ve been enjoying the benefits of that.

If now your contemplating pushing time and effort into your present batteries what is your goal? Are you hoping for one more trouble free season, perhaps two?

Me, I’d use that same time and effort to disconnect, remove and replace your current batteries with fresh ones at the start of next season and go enjoy seven more years of trouble free batteries like you’ve just had.

Then in the future you can be the envy of everyone at the dock as you tell the tale of nine, ten, twelve, fourteen years of never having a problem with your batteries. Folks will touch you for luck!

 

[Automaticman865]

Harbor Freight makes a conductance tester for batteries. Digital Battery Analyzer Cen-Tech Item#66892.
This does a great job of showing your Battery Voltage, cranking amps, internal battery resistance and percentage of whats left in it. I had one of my older agm's , 1100 cranking amps on label. Enter that into the tester and withing just a few seconds it showed it had only 230 cranking amps out of the 1100.
Whats nice about this unit is that its small and you can bring it to the store and test new batteries right on the shelf before you buy them. Thus picking out the best ones.

Stuart

 

[stwendl]

I have two versions of them and one thing they don’t do is tell you the capacity. I had a better that checked out on both those devices. It charged fine within minutes but when I put an actual load on it it was just 1% of the original capacity

These device are like looking a the fill level of a bottle of water. But if you fill the bottle with San first and then add water you can have an aparently full bottle but with less water in it

Those meters tell you SOC but not capacity that’s why you have to tell them AH. The only way to tell capacity is to discharge at a certain rate and temperature, basically emptying the bottle and measure how much liquid is in it

 

[Osprey]

Thanks for the number of useful responses to my post - all good. The post by tugnaaweight has me thinking about age - as much mine, as the batteries'. I will be 79 next boating season. Will I be still boating 7 years from now? Am I going to get a "lifetime" warranty? However, the prudent plan would be to start searching for 4 new batteries.

 

[knotflying]

Thanks for the number of useful responses to my post - all good. The post by tugnaaweight has me thinking about age - as much mine, as the batteries'. I will be 79 next boating season. Will I be still boating 7 years from now? Am I going to get a "lifetime" warranty? However, the prudent plan would be to start searching for a new set of 4 new batteries.

Save yourself a good amount of money and go with four flooded Walmart group 27 for about $90.00 each. I change mine every 3 years regardless of condition. As you said, at your age why go long, go on the 3 year economy plan! 😀 Just remember to change your charger settings and the solar panel controller settings if you have one.

 

[tugnnaweigh]

Me, I’m 62 and In the past I’ve been oriented towards getting the last troublesome year of service out of batteries or the last 5,000 unsafe miles out of a set of tires and I paid the price again and again in time, trouble and inconvenience.

Now in my Golden Years I try for Life Without Trouble and as Boating can be Trouble I push into preventing Boating Trouble pretty hard as a Larson 29’ I repowered was so much Boating Trouble the Wife called it That Damn Boat and wouldn't go aboard and I missed her.

I kept showing her Ranger Tugs until she said they seem Nice and we bought our R25 then after a few years I parked stern to stern with a R29 until she said it seems Nice and here we are today in a new to us R29.

In going from the R25 to the R29 I put eight new tires on the trailer, six running and two spares and I’ll change them out in five years or the first hiccup. I’m told the batteries are in their second year of service so anywhere in or after the fifth year or at the first hiccup I’ll change all them out.

I spend a bit of money when and where I choose instead of spending a lot more somewhere I would rather not.

My goal is to not have any of our future Boating Adventures interrupted or curtailed or cancelled or changed as boating without any of these is the memories I want to make and adventure enough for both of us.

(The secret plan is to sell the house when the Wife retires and sail away on that R41.)

 

[Dale777]

I would like to echo what tugnnaweigh said,

"I spend a bit of money when and where I choose instead of spending a lot more somewhere I would rather not.

My goal is to not have any of our future Boating Adventures interrupted or curtailed or cancelled or changed as boating without any of these is the memories I want to make and adventure enough for both of us."

With this reasoning in mind, I just pre-emptively replaced factory installed 5 year old batteries that have been trouble free. I don't want to wait until they fail while I am out cruising somewhere. If they failed when on a cruise, I might face a tow, delay in cruising plans waiting to have new batteries installed, and additional costs.

 

[andrewman]

You definitely don't want to wait until the batteries will die. That happened to me once in winter and can still remember how much trouble it caused 🙂 I have read before that batteries can sometimes show wrong values during products. If you are have any after market parts.