Charging a deep cycle AGM battery

JumbleDuck

JumbleDuck

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I've just bought a "Yuasa REC36-12 Cyclic Deep Cycle Battery 12V 36Ah" from Tayna to use with my crew's trolling motor. Do AGM batteries need any particular care when charging or is a normally car battery charger fine?

PS Ordered at 15.44 yesterday, arrived at 09.20 today, in a rural area of SW Scotland. Impressive service from Tayna, as ever.
 
Many car battery chargers have an AGM setting these days which provide for a slightly lower float voltage once the battery is fully charged. A car battery charger without an AGM setting will be fine for charging the battery but, to be on the safe side, it would be best not to leave it on charge for a long time once it has achieved full charge.

Richard
 
JumbleDuck said:
I've just bought a "Yuasa REC36-12 Cyclic Deep Cycle Battery 12V 36Ah" from Tayna to use with my crew's trolling motor. Do AGM batteries need any particular care when charging or is a normally car battery charger fine?

PS Ordered at 15.44 yesterday, arrived at 09.20 today, in a rural area of SW Scotland. Impressive service from Tayna, as ever.
Click to expand...

Its a sealed valve regulated battery. I guess you have to be careful not to overcharge ...... rather depends what you mean by a "normal" car battery charger. You'd want one suitable for AGM / VRLA batteries

Tech data sheet for the battery here https://www.yuasa.co.uk/yuasa/datasheet/index/sku/REC36-12I/

I learnt not to have a "lie in" if expecting a battery from Tayna ... good service much appreciated but a battery arriving early can be a bit of a passion killer.
 
Many thanks, everyone. I have a range of car battery chargers ranging from 3.7A ones from Lidl to a brute of a starter/charger. It sounds as if for out initial experiments it will be OK to use one of the simple ones, but disconnect when it's fully charged.

I left one of them on the DS battery earlier this year, unaware that one cell in the battery had died (silly me, I wondered why starting was poor) and it so successfully kept on charging that when I found out the vent plates had both blown off the top of the battery and the dud cell was completely dry. I think I got off quite lightly.
 
JumbleDuck said:
PS Ordered at 15.44 yesterday, arrived at 09.20 today, in a rural area of SW Scotland. Impressive service from Tayna, as ever.
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I ordered 4 x Trojans from Tayna Wednesday last week, they were delivered to Algarve Express next day and in Almancil Portugal on Monday. Couple of weeks ago, a mate posted letter from UK, took 10 days to my Portuguese address.
 
Assuming you are not in a hurry to recharge the new battery the safest option is a slow charge. An amp meter checking actual charge current will give you an idea of how the charge is going and you can estimate just how much charge you have put in compared to the 36AH rating. So use your smallest charger and be ready to stop charging when you reckon it has had enough. That is unless you have a sophisticated auto charger which will cut back current when the time comes. ol'will
 
JumbleDuck said:
PS Ordered at 15.44 yesterday, arrived at 09.20 today, in a rural area of SW Scotland. Impressive service from Tayna, as ever.
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I would respectfully suggest that it is not so much Tanya that is impressive, but the firm that did the delivery that deserves the congratulations. All Tanya did was stick it in a parcel and call the delivery co to collect. Nothing hard in that
the delivery company probably had to get it half way across the country from depot to depot and then on to a delivery driver and to you door on a pre arranged day and possibly time, all for a few £'s -------now that is impressive
 
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Unless you have a specific AGM charger, you will NOT get the life expectancy from the AGM battery that you hope for. AGM has some very specific charging requirements, if you don't stick to them, they die quite quickly, as a normal charger will leave them undercharged. A lot of "Stop/Start" car batteries were AGM, manufacturers are moving over to EFB, as it is a lot easier to charge.

Connecting an AGM to a standard "constant voltage" dumb charger is not going to get you good results. You need a 14.8V charge (yes, 14.8, not 14.2 like a standard battery charger) in order to fully charge them. If you don't *fully* charge them, they die pretty quickly.

You need a 13.65V float charge *not* a 13.8V float charge. Float them at 13.8 and again, they die pretty quickly.

There is a good writeup here:

http://www.aandncaravanservices.co.uk/agm-batteries.php

It explains why people are not getting good results when connecting AGM to a standard alternator system.

and a good writeup here an why an EFB would have been a better choice:

http://www.aandncaravanservices.co.uk/battery-technology.php
 
rszemeti said:
Unless you have a specific AGM charger, you will NOT get the life expectancy from the AGM battery that you hope for. AGM has some very specific charging requirements, if you don't stick to them, they die quite quickly, as a normal charger will leave them undercharged. A lot of "Stop/Start" car batteries were AGM, manufacturers are moving over to EFB, as it is a lot easier to charge.

Connecting an AGM to a standard "constant voltage" dumb charger is not going to get you good results. You need a 14.8V charge (yes, 14.8, not 14.2 like a standard battery charger) in order to fully charge them. If you don't *fully* charge them, they die pretty quickly.

You need a 13.65V float charge *not* a 13.8V float charge. Float them at 13.8 and again, they die pretty quickly.

There is a good writeup here:

http://www.aandncaravanservices.co.uk/agm-batteries.php

It explains why people are not getting good results when connecting AGM to a standard alternator system.

and a good writeup here an why an EFB would have been a better choice:

http://www.aandncaravanservices.co.uk/battery-technology.php
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I'm not sure this is quite right and it is certainly out of step with Victron and Mastervolt.

First, no I don't think one does need 14.8V to charge, rather that is around the top end for a fast charge in normal temperatures of 25C. In warmer conditions, and certainly proximate to a hot engine installation, this is too high. The normal AGM charging voltage is 14.2-14.6V. Also, as a rule AGMs don't like being rushed!
https://www.victronenergy.com/upload/documents/Datasheet-GEL-and-AGM-Batteries-EN.pdf

Similarly, the recommended range for float voltage is 13.5-13.8V and 13.65V just happens to be the mean.

Finally, for long-term storage (i.e. any extended period of time), the float voltage should be somewhat reduced: 13.2-13.5V is recommended. The same applies to most lead batteries.
 
Daydream believer said:
I would respectfully suggest that it is not so much Tanya that is impressive, but the firm that did the delivery that deserves the congratulations. All Tanya did was stick it in a parcel and call the delivery co to collect.
Click to expand...

Of course, but Tayna had to process the order, pack the battery (possibly filling it first) and get it in the courier's hands in time for the first delivery next day.
 
dom said:
I'm not sure this is quite right and it is certainly out of step with Victron and Mastervolt.

First, no I don't think one does need 14.8V to charge, rather that is around the top end for a fast charge in normal temperatures of 25C. In warmer conditions, and certainly proximate to a hot engine installation, this is too high. The normal AGM charging voltage is 14.2-14.6V. Also, as a rule AGMs don't like being rushed!
https://www.victronenergy.com/upload/documents/Datasheet-GEL-and-AGM-Batteries-EN.pdf

Similarly, the recommended range for float voltage is 13.5-13.8V and 13.65V just happens to be the mean.

Finally, for long-term storage (i.e. any extended period of time), the float voltage should be somewhat reduced: 13.2-13.5V is recommended. The same applies to most lead batteries.
Click to expand...

Many thanks. For the moment we're just looking to charge it for testing. Longer term we may buy an AGM charger, and then we have to work out how to charge it on the boat ...
 
Does it not occur to anyone to see what Yuasa say?
https://www.yuasa.co.uk/rec36-12.html

Charge Voltage
Float charge voltage at 20°C (V)/Block 13.65 (±1%)
Float charge voltage at 20°C (V)/Cell 2.275 (±1%)
Float Chg voltage tmp correction factor from std
20°C (mV)
-3
Cyclic (or Boost) charge Voltage at 20°C (V)/Block 14.52 (±3%)
Cyclic (or Boost) charge Voltage at 20°C (V)/Cell 2.42 (±3%)
Cyclic Chg voltage tmp correction factor from std
20°C (mV)
-4
Charge Current
Float charge current limit (A) 9
Cyclic (or Boost) charge current limit (A) 9
 
14.8v boost is too high. AGM's live happily at 14.6v boost and 13.6v float, same voltages work perfectly OK for SLA, so the two exist side by side using the same charger.
 
PaulRainbow said:
14.8v boost is too high. AGM's live happily at 14.6v boost and 13.6v float, same voltages work perfectly OK for SLA, so the two exist side by side using the same charger.
Click to expand...

14.8 is within the 3% of 14.52 which Yuasa reccommend.
The question is perhaps correctly deciding when to flip from boost to float?
 
dom said:
Link to Yuasa post #2; precise specs for batt, post #4!

Victron general AGM parameters post #12
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Seems reasonable.

What I would say is that simply hooking them up to a "halfords" bog standard charger and expecting it to work out happily is unlikely. The "motorhome" guys have been through this pain aleady.
 
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