Best bang for the buck tool for battery buying.

JohnnieB

Lead-Acid batteries have been around for over 150 years, so the arts and sciences of manufacturing them are well known throughout the battery manufacturing industry and in the past few decades corporate emphasis leans more toward the profit margin than quality, so the end product is the aggregate sum of materials supplied by the lowest bidders. Due to this, I believe there is more differences between the different grade batteries from the same manufacturer than there are differences between the same grade battery from different manufacturers.

In other words, regardless of brand name, a premium grade battery will last longer than an economy grade battery, but the price differences between super-premium, premium, standard, economy and super-economy grades isn't linear. Fortunately, there is a correlation between average SoC maintained and the number of charge cycles to be expected, which in turn can be projected into a lifespan estimate.

Unfortunately, the four golf cart battery manufacturers that publish average SoC vs charge cycle data vary quite a bit as to how many cycles equate to what average SoC. (See attachment-1) The chart I made is a yardstick rather than a caliper and not all batteries are made by the four manufacturers I have data from, so I used the average number of cycles from all four manufacturers to determine projected lifespans.

I made a chart for 6V, 8V and 12V batteries with a separate range of AH ratings for each voltage, starting with the lowest AH commonly available for each voltage up to the highest in 5AH increments. I discharged the lowest AH battery in each voltage to 50% SoC.

To use the chart, find the voltage and AH rating of the batteries you are considering to buy and divide the total cost of the batteries by the months of estimated lifespan to get the monthly cost for comparison.


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Personally, the next time I buy batteries, I'll use this cart or something similar, but I'll most likely go with a name brand unless the lesser know brand is a whole lot cheaper and the less performance is acceptable.

Attached Images

	SoC vs Lifespan.jpg (127.8 KB, 0 views)
	Battery life by AH.jpg (364.7 KB, 0 views)

BGW

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dundeebarnbuggy

Interesting and informative as always Johnnie! There is lots of "reports" here of how long everyone's pack lasted, but VERY little reports of actual number cycles, at what depth of discharge and average amp draw of the cart during the reported lifespan. Please correct me if I am wrong, but all this, along with extremely hot weather will have a big influence on life cycles.

JohnnieB

Not many cart owners have the time or dedication to keep such records, but some fleet operators might. IIRC, cartboy kept some pretty good records about battery failures in a current and a previous RXV fleet. Of course, the data only applies to those carts with those batteries at that golf course.

Attached are a couple items that delineate temperature vs longevity, but the numbers ought to be considered as trends rather than hard facts. Basically, batteries have better performance with a shorter usable lifespan in warmer climates and the opposite happens in cooler climates.

The same is true of the months listed on the chart I made. Basically. I'm trying to quantify a trend. That being higher AH batteries will have a longer usable lifespan than lower AH batteries when they are subjected to the same environmental conditions in the same cart and same maintenance. In other words, with all the variables eliminated except the AH differences. Even then, the lifespan estimated is very likely to be optimistic in most cases and pessimistic in only a few cases.

The sole purpose for the tool is to compare monthly battery costs when the AH and price are know.

Attached Images

	Battery life Expectancy Zones.jpg (162.3 KB, 0 views)
	Temperature vs storage capacity and lifespan.jpg (116.9 KB, 0 views)

dundeebarnbuggy

Thanks. I kinda laughed at the "low" temp warning. If only we could leave every motor vehicle parked [cart included] when it starts to get cold.

Mooncarter

I just bought these. If I am understanding your chart Johnnie, they are expected to last only ten months less than the most expensive.

I can get them for $540 plus tax with cores. Around here The Trojans etc. Are about twice that price. I can't justify buying them when I don't expect them to last twice as long.

Attached Images

IMG_20190209_183203645.jpg (302.4 KB, 0 views)

kgsc

I just replaced the T875s in my Yamaha yesterday. Were the original ones from when the cart was new. 2012 model. Were still working but it was time.

JohnnieB

I spent some time in Alaska and lived in Michigan for many years, so I got chuckle out that chart also.

JohnnieB

Not many people go to the top of the 8V chart (205AH) for 8V batteries. Your 170AH battery is pretty much the standard for a 6x8V battery pack and those that need/want more range usually don't go above 190AH since the 204AH from Trojan and the 205AH from US Battery are outrageously priced.

Based on the info you provided your estimated battery expense is about $12.36/mo, while the 205AH at twice the price would be about $20.26/mo, or about a 64% higher operating cost on batteries alone.

Wish I could find deals like that in my neck of the woods.

JohnnieB

Only seven years, they were just getting broken in good.

yurtle

I have a question. It may not be quantifiable unless someone has done a real comparison. Do batteries sulphate more quickly with lower SOC than with higher SOC? Assuming same quality batteries. The charts of SOC vs. years of use is based on something, though the studies backing them up are likely proprietary.

Reason I'm asking is, would someone with a lower Amp-Hr battery who goes down to 50% SOC, but then immediately recharges be better, worse, or the same (or unquantifiable) as someone with a higher Amp-Hr battery that only goes down to 70% SOC, but waits several hours before charging?

I guess what I'm asking is which is worse, short term low SOC, or longer term higher SOC?

Ignoring cost, we'd all have the highest Amp-Hr battery, which would keep a higher SOC than a lower Amp-Hr battery, but as you pointed out, the life cycle cost tips the choice away from the highest Amp-Hr, best quality. Just wondering if driving habits make enough of a difference to even notice?