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Can I substitute a 12 V 10 Ah sealed lead acid battery for the 12 V 7 Ah one supplied with my Gallagher S100 solar energizer (for an electric fence)? Gallagher does not offer this kind of technical advice. In principle, would the higher amperage have any negative effect?

winny
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Bob
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5 Answers5

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10Ah means that IN THEORY the battery can supply 10A for 1 hour, or 5A for 2 hours, etc. It's the CAPACITY of the battery. As noted in the comments, the actual amount a specific battery can deliver is a given period of time varies based on its design and construction. But at some discharge rate you should be able to have it do so for some period of time such that [discharge rate] x [time] = [amp hour rating of the battery]

So going from a 7Ah to a 10Ah will be fine as long as the larger battery fits as for the most part, a larger capacity battery will be physically larger.

It is usually indirectly related to the amount of current the battery can safely supply but this is not a hard-and-fast rule. You'd need to inspect the specs for the battery to be sure. Generally, however, the larger the Ah capacity of a given battery, the larger current it can supply. This does NOT mean that your load will draw more current though.

You could have a 1000Ah battery and if your load only requires 0.1mA it will draw no more than that.

jwh20
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    Actually a 10Ah battery will give much less than 1 hour at 10A or much less than 2 hours at 5A. The battery Ah rating is usually the 20 hour rating, so it can give 0.5A for 20 hours as per the specs. – Justme Mar 08 '22 at 21:20
  • @Justme surely that will be more time than the 7AH battery originally fitted... – Solar Mike Mar 08 '22 at 21:56
  • It just depends on the specific battery. – jwh20 Mar 08 '22 at 22:23
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We could try to do some PhD level work here on your question but the most likely answer is yes, the 10 Ah battery will work fine in place of the 7 Ah battery. There could be some obscure reasons why it might not work well, etc, but I think I would advise you to just give it a try and see how it goes. I feel 95 percent confident that it will work well enough.

user57037
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The quality of a lead acid battery is measured by several metrics.

  • Capacity [Amp-hr or Ah] {short term 20h}
  • CCA [Amps @ 0 deg] a function of sustained ESR for 30 s.
  • Self discharge time ... depends on age, health and chemistry of battery
  • weight due to lead plate thickness
  • deep cycle type

In each "case", more is better, while other variables still matter and affect cost. There are a number of different designs to cost-reduce quality.

Tony Stewart EE75
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  • I do not feel that CCA is very important for the use case discussed here. – StarCat Mar 09 '22 at 11:24
  • True but this measures the ESR of the battery to surge demands and thus voltage load regulation error due to a short circuit from fence invasion.. I mentioned these parameters for all uses. – Tony Stewart EE75 Mar 09 '22 at 15:30
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The rule-of-thumb, for an optimum match between solar panel Watts and battery Ah, is 1:1 (1 W to 1 Ah).

The Gallagher S100 solar energiser does follow the rule-of-thumb (7 W solar panel charging a 7.2 Ah battery).

Using a 10 Ah battery would have no negative effect.

There would be no positive effect either, since the 10 Ah battery cannot charge to a capacity higher than what the 7.2 Ah can.

vu2nan
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  • Are you sure about that? Most SLA chargers I know will charge until the battery does not accept any more charge (i.e. charging current drops below a certain threshold), regardless of the capacity. For a 10Ah battery this will mean it will get fully charged, but it will just take longer. – StarCat Mar 09 '22 at 11:21
  • Average output voltage of a 12 V solar panel being 14 V, average output current from the 7 W panel would be 0.5 A. The Gallagher S100 Solar power fence energiser can work for 3 weeks, on a fully charged 7.2 Ah battery, without sunlight. One may conclude that, considering the very low battery drain and 5 hours / day of peak sunlight , the solar panel would only be topping up the charge of the battery. The scenario would be the same with a 10 Ah battery with the only difference being that its full charge would last for 4 weeks without sunlight. – vu2nan Mar 09 '22 at 12:01
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Short answer: Yes

You can substitute the battery (7.2Ah >>> 10Ah) and you will have ZERO issues.
Just check if dimensions fit perfectly!

According to Gallagher manufacturer datasheet, using original 7.2Ah:

enter image description here

So the charger can recharge the battery - same 12V rating - with a bigger capacity, being protected from an undervoltage event that could damage any SLA battery life.
An important point here is that 43mA x1h = 43 mAh or x 24h = 1A.Day
From 7.2Ah to 10Ah, the new battery will last longer, even if sun is not available. Proportions assumed and probably enabling some energy saving features as night-mode, etc., it may last about 30 days.

About the Solar panel and charging: above site confirms to use a 7 Watt panel. Specs of similar 7W model says:

  • 7W total output, 15-17 volts, and 583mA current.

So, let’s say the maximum current can be as high as 0.5A; this means C/20 for a 10Ah battery and it is a nice slow charging current.
So, no problem here too, assuming the manufacturer already has an adequate charger circuit inside - for instance compensating for the ambient temperature fluctuations along the year.

Finally, the charging capability would be related to the total amount of solar energy available and how appropriate the solar panel Wattage is to capture enough electricity for the device.
If the battery is too slow to recover to a healthy voltage, you might consider repositioning the panel or eventually upgrading the panel total Wattage - but that would be another question to be answered.

I hope it helps.

EJE
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