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I just bought this battery:

Specifications of Bosch motorcycle battery

So what does the 75A mean? How do I get the same parameter "10hr" that appears in this question: Whats does "hr" mean among "V" and "Ah" in batteries?

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  • \$\begingroup\$ Google “lead acid battery CCA”. \$\endgroup\$ – winny Sep 13 '18 at 17:04
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    \$\begingroup\$ @winny this is not a starter battery with CCA. It is deep cycle rated in amp hours not CCA. \$\endgroup\$ – Misunderstood Sep 13 '18 at 18:12
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    \$\begingroup\$ @Misunderstood It’s 5 Ah. 75 A may not be the CCA rating in this case, but it’s a good term for OP to understand about batteries and peak current ratings. \$\endgroup\$ – winny Sep 13 '18 at 20:21
  • \$\begingroup\$ @winny I agree. A battery with this capacity is more a motor scooter battery. A deep cycle general purpose battery has the capacity to source 75 amps which is sufficient to start a 90cc engine. The CCA only requires a minimum of 30 seconds at 0°C. \$\endgroup\$ – Misunderstood Sep 13 '18 at 22:42
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The 75A is the rated current the starter may draw for a few seconds without damaging the battery.

There's no discharge rating printed on the battery. Bosch usually uses a 20hr rating for the capacity, it seems. At 10hrs, it's 90% of the printed capacity.

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    \$\begingroup\$ My suspicion, offered without proof, is that 5AH might well mean 5 Amp Hours. \$\endgroup\$ – Scott Seidman Sep 13 '18 at 17:12
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    \$\begingroup\$ Yes, at 20 hours discharge duration. That's what Bosch uses for their other sealed lead batteries. I haven't found the datasheet for this one, unfortunately. At 10 hours, they derate to 90% of the printed capacity. \$\endgroup\$ – Janka Sep 13 '18 at 17:14
  • \$\begingroup\$ @ScottSeidman indeed 5AH = 5 amp hours. \$\endgroup\$ – Misunderstood Sep 13 '18 at 18:15
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    \$\begingroup\$ Battery amp hour capacity is base on a 5 hr or 20 hr discharge rate. If both are not specified it is safe to assume it's a 20 hr discharge as it will be longer than a 5 hr. I have no idea what you mean by: "At 10 hours, they derate to 90% of the printed capacity." this makes no sense. \$\endgroup\$ – Misunderstood Sep 13 '18 at 18:19
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    \$\begingroup\$ @Misunderstood: the Bosch RBT5A is a motorcycle starter battery. It even has a motorcycle on the cardboard box: vn-live-02.slatic.net/p/8/… \$\endgroup\$ – Janka Sep 13 '18 at 21:59
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A battery of this size is classified as a power sports battery. CCA is not applicable to powersports batteries. A small single cylinder engine (≈120cc or less) uses a low torque starter motor that takes like 20 amp to turn over.

The Bosch M designation, in M6, is for Marine. Marine batteries have a dual role as starter and deep cycle. Bosch no longer sells an M6 battery but still sells an m4 and M5 as marine batteries.

Bosch only sells Li-ion powersports batteries and no longer sells a powersports SLA battery, except in third world countries and began marketing them in Indonesia in 2017. It was confirmed this is a rugged general purpose deep cycle battery. In this capacity it does not make sense to manufacture a deep cycle, marine, and powersport when one battery covers all markets.

Some retailers have standard tables for lead acid batteries which includes a row or column for CCA. They will use the deep cycle's max current as the CCA because technically the battery can supply 75 amp for 30 seconds, much longer actually.

I also confirmed that AH rating is no longer used for automotive batteries. Car batteries sold in the US only have CCA and Reserve Capacity (RC) is the number of minutes a fully charged battery at 80°F will discharge 25 amps until the battery drops below 10.5 volts. I also confirmed this by buying a Duracell Ultra (SLI-78M) truck battery. The only specs on it are CCA (800) and RC (115 minutes).

RC used to be rated in AH but was too confusing because the AH rating was specified between 5-20 AH. AH is no longer used in automotive batteries for RC. It is still used in powersports batteries. Powersports batteries are switching over to general purpose Li-ion rather than relabeling their deep cycle SLA.

While this battery is a powersports battery marketed in countries where the typical transportation is moped and motor bikes, it made no sense to design another box with a moped rather than a crotch rocket for a low end product.

It is marketed by Bosch as a powersports battery and sold by retailers as a motorcycle battery.

If the 75A were CCA that would mean it is a measurement of the number of amps a battery can deliver at 0°F for 30 seconds and not drop below 7.2 volts.

CA (not cold CA) is cranking amps measured at 32°F and also called marine cranking amps (MCA).

Battery Stuff also confirms I was correct.

75A means this is the maximum discharge rate that will not damage the battery.

This battery is likely not a motorcycle starter battery but rather a deep cycle. This appears to be for a lightweight electric vehicle like a kids car. 5AH is not much capacity for a Sealed Lead Acid (SLA). The batteries used in a golf cart will typically have at least 100 Amp Hour capacity.

Lead Acid batteries are Starter or Deep Cycle.

Starter batteries (cars, trucks, motorcycles) are usually rated in CCA (cold cranking amps).
Deep Cycle are commonly used for solar power, UPS backup, and electric vehicles rated in Amp Hours (AH).

Because this battery is rated in AH, it is a deep cycle

My Harley Road King needs 400 CCA. If I tried starting my bike with this battery it would kill it because it would exceed the 75A max. Conversely if I connected my Harley battery to my solar power system it would die after about 10-12 deep discharge cycles.

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  • \$\begingroup\$ @Misunderstood Since you've done some research into these Bosch batteries, were you able to find a datasheet? 75A can mean one of two things. (1) If this is touted as a starter battery, then this is cranking amps. (2) If this is a touted as a deep cycle battery, then this is the current at which is achieves its capacity (Ah) rating. Capacity is current-dependent: at lower current a battery has a higher capacity. Having said that, it looks strange that a deep cycle battery would be rated at a current which it can sustain for only four minutes. \$\endgroup\$ – Nick Alexeev Sep 16 '18 at 2:15
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    \$\begingroup\$ @NickAlexeev It is rated at 5 AH with no CCA. This reserve capacity is generally done at 0.05C for 20 hours. That is why the RC was changed to minutes at 25 amp for starter batteries. The max current is 75 amp generally measured a 3C, which will not damage the plates of a deep cycle SLA. No, I could not find a datasheet so I called Bosch in Illinois. Read the link in my update. It confirms what I said is true as well as the manager of Batteries+ and the rep at Bosch. \$\endgroup\$ – Misunderstood Sep 16 '18 at 2:44

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